The present invention relates to a slide type miter saw, and more particularly, to such a miter saw whose circular-saw unit is movable frontward and rearward and pivotally movable up and down with respect to an upper surface of a base.
Hitherto, a slide type miter saw having a base and a circular-saw unit has been known. The circular-saw unit is movable frontward and rearward and pivotally movable up and down with respect to an upper surface of a base. A workpiece is mounted on the upper surface of the base to be cut with a circular saw blade provided in the circular-saw unit. Laid open Japanese Patent Application Publication No. 2001-300901 discloses a miter saw having a stopper that defines the lowermost position of the circular-saw unit, thus preventing the circular-saw unit from excessively moving downward into the base.
Generally, a slide type miter saw cuts a workpiece in such a way as is depicted in FIG. 33. The miter saw 101 has a base 110 and a circular saw blade 121. In FIG. 33, the back of the base 110 is shown on the left, and the front of the base 110 on the right. While the circular saw blade 121 rotates clockwise as seen in FIG. 33 the circular saw blade 121 moves from the front of the base 110 toward the back of the base 110, to cut the workpiece W held on the base 110. This method of cutting the workpiece W is called “upper cutting.” A cutting force is applied in the direction in which the wood fibers move away from the workpiece W. Inevitably, fluffs and edge cracks will be generated at the upper surface of the workpiece W. Reducing fluffs and edge cracks as much as possible is important, particularly in cutting decorative plywood plates that should preserve good outer appearance.
To reduce fluffs and edge cracks, the workpiece W is positioned such that its obverse surface contacts the base 110, thus mounted upside down on the base 110. In this case, the miter saw 101 performs “down cutting” at the obverse surface of the workpiece W facing the base 110. In this method, however, the obverse surface of the workpiece W faces downwards. Consequently, the user of the miter saw 101 cannot observe a cutting line provisionally marked on the obverse surface of the workpiece W. Thus, the user may often fail to align the circular saw blade with the cutting line.
Another method for reducing fluffs and end cracks has been proposed in which a very shallow groove is provisionally formed along the cutting line in the obverse surface of the workpiece W. If the workpiece W is cut along this groove while the groove is positioned at the upper surface, generation of fluffs or edge cracks can be restrained in the upper surface of the workpiece W, in spite of the force acting in the direction in which the wood fibers move away from the workpiece W.
Another cutting method, known as “groove forming” has been practiced hitherto. In this method, a groove of a desirable depth, not a shallow groove, is cut in the obverse surface of the workpiece. Laid open Japanese Patent Application Nos. H6-71603, H11-34002 and H4-201011 disclose slide type miter saws that can easily accomplish the groove forming. These miter saws are provided with a stop device as well as the stopper. The stopper defines the lowermost position of the vertically movable circular-saw unit so as to prevent the circular-saw unit from excessively moving downwards for cutting the workpiece into two pieces. The stopper device is adapted for regulating a vertical position of the circular saw unit in order to form a groove of a desired depth in the upper surface of the workpiece.
The stop device includes an adjusting bolt. The adjusting bolt is turned to control a depth of the groove in the upper surface of the workpiece W so as to provide a groove of a desired depth. With these miter saws, the stop device for forming a groove can be switched between an operative state and an inoperative state. Thus, each miter saw can be switched between the groove-forming mode and the workpiece-cutting mode.
According to the laid open Japanese Patent Application Publication Nos. H6-71603 and H11-34002, if the groove forming is to be performed on a thin workpiece, the adjusting bolt of the stopper device must be held at a relatively high position and the circular-saw unit is held at a low position, in order to form a groove in the upper surface of the thin workpiece. On the other hand, if the workpiece is thick, the adjusting bolt must be held at a relatively low position and the circular-saw unit is held at a high position, to cut a groove in the upper surface of the thick workpiece. Therefore, large moving stroke of the adjustment bolt is required, and as a result, much labor and time are required to operate the miter saws.
In the miter saw disclosed in the laid open Japanese Patent Application Publication No. H4-201011, the stopper device has a plurality of steps to provide a plurality of stop positions. Hence, a groove can be easily formed in the upper surface of the workpiece to various depths dependent on the selection of one of the steps. However, the adjusting bolt of the stopper device must be moved back to a position equivalent to the lowermost position of the circular saw unit each time the circular-saw unit is to be moved to its lowermost position for the workpiece cutting mode. Such work for moving the adjusting bolt is cumbersome. Such cumbersome work may also be necessary in order to form a shallow groove in the obverse surface of the workpiece to reduce fluffs and edge cracks as described above.